1. Field of the Invention
The present invention relates to a display gas discharge screen for displaying a matrix of luminous points.
More particularly, the present invention relates to a structure of a matrix of plasma cells corresponding to respective luminous points, which is self-scanned by means of a first plurality of parallel electrodes and which displays the luminous points by means of a second plurality of electrodes parallel to the first plurality of parallel electrodes, said first and second pluralities of electrodes being perpendicular to a third plurality of parallel electrodes.
2. Description of the prior art
The both essential functions, namely, scanning function and displaying function, are incorpored distinctly in the prior art display screens.
In a first prior art display screen, it utilizes the glow discharge phenomenon resulting from the application of electric fields to one or more inert gases possessing negative inpedance characteristics and, therefore, inherent memory. An initial set of signals defining a desired on/off pattern are applied to both single pluralities of electrodes. Maintenance of the resulting glows is achieved by the application of a non-information-bearing sustain signal sequence of lesser magnitude than these signals used for writing the information in the first instance.
In this end, each gas cell is defined by the intersection of both perpendicular electrodes respectively of both pluralities of electrodes. The discharge of plasma atmosphere occurs in the cell when a sufficient potential difference exists between these electrodes. Therefore, the scanning and displaying functions are achieved only with these two electrodes.
For the construction of a such screen, it is necessary to superpose a first plurality of coplanar parallel electrodes perpendicularly to a second plurality of coplanar parallel electrodes. In addition, for providing the displaying function of the screen, or the memory function, at least a dielectric substrate is positioned between these two pluralities of electrodes.
In a second prior art display screen, the scanning and displaying functions are achieved respectively with first and second pluralities of parallel electrodes and in common with a third plurality of parallel electrodes perpendicular to first and second plurality of electrodes. In this case, a cell is ionized, and its adjacent cell of the same line of cell matrix is preionized at the same time by means of scanning pulses applied between a first and a third corresponding electrodes. This preionization serves eventually at the display of the corresponding luminous point by means of displaying pulses applied between a second and a third corresponding electrodes.
As the first case, this prior art screen includes a great thickness of the screen resulting in the superposition of different pluralities of electrodes and dielectric substrats. In addition, the certain electrodes obscure the glows issued to the cells, and therefore, reduce the efficiency of the screen.
Further the superposition of electrodes requires an expensive structure of very difficult construction.